Computers are used for many different tasks in a variety of environments. For example, computers are used in people's personal lives to conduct financial transactions and communicate private thoughts. Computers are also used in professional environments to share vital business information, collaborate on technical projects, exchange business plans, and so forth. In many such cases, people prefer to protect the underlying data by limiting access to it.
In other words, people often prefer to maintain the confidentiality of the data that is being exchanged, shared, stored, etc. using some mechanism. Such mechanisms often involve encryption because access to encrypted data may be limited. Unencrypted data is encrypted using an encryption key to produce encrypted data. To access the encrypted data, the same or a cryptographically-related encryption key is used to decrypt the data. The decrypted data may then be accessed in standard manners.